1 | /* |
2 | * Copyright (c) 1995-1999 by Internet Software Consortium. |
3 | * |
4 | * Permission to use, copy, modify, and distribute this software for any |
5 | * purpose with or without fee is hereby granted, provided that the above |
6 | * copyright notice and this permission notice appear in all copies. |
7 | * |
8 | * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS |
9 | * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES |
10 | * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE |
11 | * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL |
12 | * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR |
13 | * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS |
14 | * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS |
15 | * SOFTWARE. |
16 | */ |
17 | |
18 | /* This file contains the definitions related to res_init which are |
19 | linked into libc instead of libresolv. */ |
20 | |
21 | #include <atomic.h> |
22 | #include <limits.h> |
23 | #include <sys/types.h> |
24 | #include <netinet/in.h> |
25 | #include <arpa/nameser.h> |
26 | #include <resolv.h> |
27 | #include <libc-lock.h> |
28 | |
29 | extern unsigned long long int __res_initstamp attribute_hidden; |
30 | /* We have atomic increment operations on 64-bit platforms. */ |
31 | #if __WORDSIZE == 64 |
32 | # define atomicinclock(lock) (void) 0 |
33 | # define atomicincunlock(lock) (void) 0 |
34 | # define atomicinc(var) catomic_increment (&(var)) |
35 | #else |
36 | __libc_lock_define_initialized (static, lock); |
37 | # define atomicinclock(lock) __libc_lock_lock (lock) |
38 | # define atomicincunlock(lock) __libc_lock_unlock (lock) |
39 | # define atomicinc(var) ++var |
40 | #endif |
41 | |
42 | int |
43 | res_init(void) { |
44 | extern int __res_vinit(res_state, int); |
45 | |
46 | /* |
47 | * These three fields used to be statically initialized. This made |
48 | * it hard to use this code in a shared library. It is necessary, |
49 | * now that we're doing dynamic initialization here, that we preserve |
50 | * the old semantics: if an application modifies one of these three |
51 | * fields of _res before res_init() is called, res_init() will not |
52 | * alter them. Of course, if an application is setting them to |
53 | * _zero_ before calling res_init(), hoping to override what used |
54 | * to be the static default, we can't detect it and unexpected results |
55 | * will follow. Zero for any of these fields would make no sense, |
56 | * so one can safely assume that the applications were already getting |
57 | * unexpected results. |
58 | * |
59 | * _res.options is tricky since some apps were known to diddle the bits |
60 | * before res_init() was first called. We can't replicate that semantic |
61 | * with dynamic initialization (they may have turned bits off that are |
62 | * set in RES_DEFAULT). Our solution is to declare such applications |
63 | * "broken". They could fool us by setting RES_INIT but none do (yet). |
64 | */ |
65 | if (!_res.retrans) |
66 | _res.retrans = RES_TIMEOUT; |
67 | if (!_res.retry) |
68 | _res.retry = 4; |
69 | if (!(_res.options & RES_INIT)) |
70 | _res.options = RES_DEFAULT; |
71 | else if (_res.nscount > 0) |
72 | __res_iclose (&_res, true); /* Close any VC sockets. */ |
73 | |
74 | /* |
75 | * This one used to initialize implicitly to zero, so unless the app |
76 | * has set it to something in particular, we can randomize it now. |
77 | */ |
78 | if (!_res.id) |
79 | _res.id = res_randomid(); |
80 | |
81 | atomicinclock (lock); |
82 | /* Request all threads to re-initialize their resolver states, |
83 | resolv.conf might have changed. */ |
84 | atomicinc (__res_initstamp); |
85 | atomicincunlock (lock); |
86 | |
87 | return (__res_vinit(&_res, 1)); |
88 | } |
89 | |
90 | /* Initialize resp if RES_INIT is not yet set or if res_init in some other |
91 | thread requested re-initializing. */ |
92 | int |
93 | __res_maybe_init (res_state resp, int preinit) |
94 | { |
95 | if (resp->options & RES_INIT) { |
96 | if (__res_initstamp != resp->_u._ext.initstamp) { |
97 | if (resp->nscount > 0) |
98 | __res_iclose (resp, true); |
99 | return __res_vinit (resp, 1); |
100 | } |
101 | return 0; |
102 | } else if (preinit) { |
103 | if (!resp->retrans) |
104 | resp->retrans = RES_TIMEOUT; |
105 | if (!resp->retry) |
106 | resp->retry = 4; |
107 | resp->options = RES_DEFAULT; |
108 | if (!resp->id) |
109 | resp->id = res_randomid (); |
110 | return __res_vinit (resp, 1); |
111 | } else |
112 | return __res_ninit (resp); |
113 | } |
114 | libc_hidden_def (__res_maybe_init) |
115 | |
116 | /* This needs to be after the use of _res in res_init, above. */ |
117 | #undef _res |
118 | |
119 | /* The resolver state for use by single-threaded programs. |
120 | This differs from plain `struct __res_state _res;' in that it doesn't |
121 | create a common definition, but a plain symbol that resides in .bss, |
122 | which can have an alias. */ |
123 | struct __res_state _res __attribute__ ((nocommon)); |
124 | |
125 | #undef __resp |
126 | __thread struct __res_state *__resp = &_res; |
127 | extern __thread struct __res_state *__libc_resp |
128 | __attribute__ ((alias ("__resp" ))) attribute_hidden; |
129 | |
130 | /* We declare this with compat_symbol so that it's not |
131 | visible at link time. Programs must use the accessor functions. */ |
132 | #ifdef SHARED |
133 | # include <shlib-compat.h> |
134 | compat_symbol (libc, _res, _res, GLIBC_2_0); |
135 | #endif |
136 | |
137 | #include <shlib-compat.h> |
138 | |
139 | #if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_2) |
140 | # undef res_init |
141 | extern int __res_init_weak (void); |
142 | weak_extern (__res_init_weak); |
143 | strong_alias (__res_init, __res_init_weak); |
144 | compat_symbol (libc, __res_init_weak, res_init, GLIBC_2_0); |
145 | #endif |
146 | |